1. Field of the Invention
The present invention relates to a ceramic electronic component and a wiring board. More particularly, the present invention relates to a ceramic electronic component suitably used while being embedded in a wiring board, and to a ceramic-electronic-component embedded wiring board in which the ceramic electronic component is embedded.
2. Description of the Related Art
With recent reduction in size and thickness of electronic apparatuses, such as mobile telephones and portable music players, the sizes of wiring boards to be mounted in the electronic apparatuses have been reduced.
For example, Japanese Unexamined Patent Application Publication No. 2001-352141 discloses a method for reducing the size of a wiring board, in which a chip capacitor is embedded in a wiring board, a through hole is formed in a portion of the wiring board above the chip capacitor with a laser, and the inside of the through hole is plated to form wiring to the chip capacitor. According to this method, it is possible to reduce the mounting area of the component on a surface of the wiring board and to thereby reduce the size of the wiring board.
However, when the chip capacitor is embedded in the wiring board, as in Japanese Unexamined Patent Application Publication No. 2001-352141, the overall reliability of the wiring board decreases.
Through intensive studies, the inventors of the present invention discovered that the chip-capacitor embedded wiring board described in Japanese Unexamined Patent Application Publication No. 2001-352141 lacked reliability for the following reasons. That is, in the chip-capacitor embedded wiring board described above, the chip capacitor is provided on a base substrate, and the chip capacitor and the base substrate are bonded with adhesive. However, since the entire wraparound portion of an external electrode contacts the base substrate, the adhesive does not properly enter between the external electrode and the base substrate, and the thickness of a layer of the adhesive becomes too small between the external electrode and the base substrate. This decreases the adhesion strength and the adhesive is not provided. As a result, a gap is formed between the external electrode and the base substrate.
Further, when the through hole is formed by a laser, a residue of resin that forms the wiring board is produced, and desmearing is sometimes performed to remove the residue of resin. During desmearing, the wiring board is exposed to a strong alkaline solution, such as potassium permanganate. In this case, the solution enters the gap and remains therein. This solution reduces reliability.